Method for producing polymeric particles



March 12, 1968 B. D. RICE 3,373,235

METHOD FOR PRODUCING POLYMERIC PARTICLES Filed Sept. 17, 1965 2 Sheets-Sheet l 5/// J. fi/ce /Z/?bf 3 INVENTOR.

MG. 246 M March 12, 1968 B. D. RICE METHOD FOR PRODUCING POLYMERIC PARTICLES 2 Sheets-Sheet 2 Filed Sept. 17, 1965 INVENTUR.

United States Patent 3,373,235 METHOD FOR PRODUCING POLYMERIC PARTICLES Billy D. Rice, Pasadena, Tex., assignor to Petro-Tex Chemical Corporation, Houston, Tex., a corporation of Delaware Filed Sept. 17, 1965, Ser. No. 487,986 9 Claims. (Cl. 264-143) ABSTRACT OF THE DISCLOSURE A method of separation of polybutene polymer from a solvent characterized by extruding the polymer at a positive pressure into an area of reduced pressure and impinging the polymer against an arcuate surface to achieve further separation by volatilization of the solvent and particulation of the filament.

This invention generally relates to a novel method for separating and removing polymer from a polymer solution. In one of its aspects, this invention relates to a method for producing and separating solid polybutene polymer particles from a solvent, and particularly from a solvent in which the polymerization has occurred. In still another aspect, this invention relates to a novel method for producing and separating free-flowing polybutene- 1 polymer particles having a high-bulk density from a solvent containing the polybutene-l.

During the production phase of polybutene polymer, the polymer is generally formed in an appropriate organic solvent such as heptane, hexane, butane, butene-2, and the like. Generally, the polymer is present in the solvent as a solution. In order to produce a commercially useful polymeric material, it is necessary to extract the polymer from the solvent. It is important that this extraction step or recovery step be carried out in the most efiicient manner possible because of the economics involved. In addition, it is important to obtain an end product which is not only free of solvent, but which is also relatively free of other low boiling contaminants. If the solvent or contaminants are not fully removed from the polybutene polymer, prior to extruding the polymer, the extruded polymeric material may contain bubbles or other imperfections. In addition, the entrapped solvent may generate combustible or explosive conditions when the polymer is extruded or if the polymer is stored for extended periods of time.

The prior art has utilized many methods for separating polymer from a solvent. For example, polymer has heretofore been removed from a solvent by precipitating it with alcohol and gravitationally separating out the polymer. One disadvantage of the precipitation method is that the polymer retains large quantities of the solvent and requires extended periods of high temperature drying to insure complete removal of the solvent.

Another method which has been used is spray drying. This technique is expensive and requires large drying equipment which normally cannot be conveniently installed in most manufacturing operations. Furthermore, spray drying is generally limited to dilute or low viscosity polymeric solutions and requires large volumes of heated gas such as air to effect complete drying of the polymer.

Another means which has been used is to flash or fractionate the solvent from the polymer solution. This technique generally requires the use of high temperatures which can result in a popcorn type polymer having a low bulk density and a broad range of particle sizes, making extrusion of the polymer difficult.

It is therefore an object of this invention to provide a method for separating polymer from a solution, which will overcome the shortcomings of the prior art noted above.

Another object of this invention is to provide a method for producing and separating solid polybutene polymer particles having an improved bulk density and uniform particle size.

Another object is to provide a process for producing polybutene polymer particles suitable for extrusion.

Still another object of this invention is to provide a method for producing and separating free-flowing solid polybutene-l polymer particles having a higher bulk density than that heretofore obtained from a solution of butene-l polymer and butene-l monomer.

Briefly stated, the novel method of the invention for separating polybutene polymer is characterized by the use of nozzle means for receiving the pressurized polymer solution and for extruding the solution to form a filament of polymer while partially volatilizing the solvent containing the polymer. Means are also connected to the nozzle means for receiving and subjecting the polymeric filaments to a force for particulating the polymer and for further volatilizing the solvent.

In carrying out the method of the instant invention, the polymer solution is normally introduced into the nozzle means at an elevated temperature and at a positive pressure. It is understood that the method of this invention also contemplates the cooling of the end product. The pressurized polymer solution is then extruded into a lower pressure environment to thereby form the polymer into a filament and at the same time to partially volatilize the solvent. The polymeric filament is then subjected to a particulating force such as that obtained when the polymeric filament is impinged against an arcuate surface. This exterior force particulates said filament accompanied with further volatilization of said solvent. In some instances, a heated gas can be added as a preferred feature of the invention.

Reference to the drawings will further explain the invention wherein like numerals refer to like parts and in which:

FIGURE 1 is a side elevation view of one embodiment of a novel separating apparatus employed in this invention.

FIGURE 2 is a side elevation view taken at line 2--2 of FIGURE 1.

FIGURE 3 is a fragmentary enlarged cross sectional view of the nozzle assembly 11 shown in FIGURE 1.

FIGURE 4 is a partial isometric view of the discharge tube 12 shown in FIGURE 1 and showing the looped section thereof.

FIGURE 5 is an alternate embodiment of a means providing an impinging surface showing a tubular member defining an arc of about degrees.

FIGURE 6 shows an alternate impingement means in the form of a channel-shaped slide member defining an open loop of about 360 degrees.

Referring now to FIGURE 1, the apparatus shown therein is generally comprised of a nozzle assembly 11 at its upper end, which nozzle assembly discharges ultimately into an impingement means in the form of a curved arcuate discharge tube 12 defining a loop. The upper end of nozzle assembly 11 is connected by appropriate connectors to an appropriate upper chamber member 13, which is adapted to receive the pressturized polymer solution. It is to be understood that means (not shown) may be provided for pressurizing and heating the polymer solution to an elevated temperature and a positive pressure. Generally, though, the polymer solution will be in a heated condition and under positive pressure, such as at least 50 p.s.i.g., as the result of the production phase wherein the polymer is produced in a suitable solvent.

Nozzle 11 is also provided with a lower connector 14 at about midpoint thereof, which'connector is attached to T fitting 15 having inlet tube 16 connected thereto for the admission thereinto of a heated, pressurized gas such as heptane, butane or butene. The lower end of T fitting 15 connects to the aforesaid discharge tube 12. It will be observed that the discharge tube 12 is of a larger cross sectional area than is the discharge orifice 17 at the lower end of nozzle assembly 11. Discharge tube 12 is in the form of a loop whereby filaments passing therethrough are subjected to an impingement action and a centrifugal force and are discharged into a convenient collection means such as cyclone receiver 18.

Referring now to FIGURE 3, the details of nozzle assembly 11 will be described in greater detail. One important feature of the nozzle assembly is that it is provided with upper nozzle 23 which is adapted to initially receive the pressurized polymer solutions from a chamber member 13 as adapted to extrude the polymer solution therethrough in a controlled and uniform rate of flow. Nozzle 23 has an axial bore 24 therethrough which communicates with chamber member 13 and intermediate tube 25. Bore 24 and bore 26 are communicated by about a 45 degree smooth edge out 29. If polymer particles of uniform size and bulk density are desired, the length of nozzle 23 should be at least times the diameter of bore 24. The preferred relationship between the length of nozzle 23 and the axial bore 24 can be conveniently represented by a length-diameter ratio of between 8:1 and 50:1 and,

' preferably, of between :1 and 40:1, and still more preferably, a length-diameter ratio of between 12:1 and 30:1. With a length-diameter ratio as set forth above, the size of polymer particles, as Well as the amount of residual solvent present in the polymer can be conveniently controlled. For example, if a polybutene-l polymer solution is pressurized to about 150 p.s.i.g. and introduced into a nozzle assembly in which nozzle 23 has a length of about 1% inches andaxial bore 24 has a diameter of between 0.039 and 0.180 inch, uniform polymer particles of solid butene-l can be obtained having a lowbulk density. However, if under the same conditions the diameterof bore 24 is decreased to below 0.039 inch, dust-like polymer particles are produced which can be easily carried overhead with the solvent vapors causing separation and purification problems. If, on the other hand, the bore size diameter is increased to above 0.180 inch, filamentary and popcorn type polymer particles are produced which are generally less desirable for feeding into an extruder. It should be understood, however, that if dust-like particles having a. diameter of between 10-40 microns are desired, the diameter of axial bore 24 can be at or even below 0.02

inch.

The lower end of nozzle 23 connects with the upper end of an elongated housing member in the form of intermediate tube 25, having an enlarged axial bore therethrough. The lower end of enlarged axial bore 26 forms the discharge orifice 17 referred to above.

While nozzle 23 and intermediate tube 25 have been described as integral units, it is to be understood that these members may be separate units, so long as they are held together in abutting coaxial alignment as shown. It is important, however, that enlarged bore 26 be of a larger cross sectional area than the cross sectional area of bore 24. Hence, when the pressurized polymer solution is extruded through bore 24 and into enlarged bore 26, the polymer solution is subjected to a lower pressure environment in bore 26. This permits the controlled expansion and volatilization of the solvent portion of the polymer I 4 solution and also permits the polymer ,to be cooled and extruded in the form of a solidified strand or filament.

In the usual operation, the polymer solution generally contains between about 5 to 40 percent by weight of the polymer and 60 to 95 percent solvent. Increased concentrations of polymer in the solvent may, however, be used if such increased concentrations do not inhibit a steady and continuous flow of polymer solution through the nozzle assembly. If, for example, solid butene-l particles are to be separated from a solution of butene-l polymer in butene-l monomer, the concentration of butene-l polymer in the monomer is adjusted, before introduction into the nozzle assembly, to a concentration of preferably between about 8 to 15 percent by weight of .the total solution.

Upon passage of the polymeric solution out of bore 24 into bore 26, the solution is partially vaporized and a mixture comprising polymer solution, solvent vapor and solid polymer is present. As previously noted, bore 26 is of a larger diameter than bore 24. This is necessary to initiate vaporization of the liquid solvent and to accelerate the flow of the mixture through bore 26 and into tube 12. In other words, the diameter of bore 24 and the diameter of bore 26 must be such that the polymeric strands which are produced from the polymeric solution are accelerated to a velocity suflicient to cause particulation of the polymeric strands upon impingement against an arcuate surface. This relationship or ratio of diameter between bore 24 and bore 26 may be referred to as the strand formation and particulating velocity ratio. When butene-l polymer, for example, is dissolved in a solvent, or preferably when the butene-l polymer is dissolved in its own monomer (butene-l), the diameter of bore 24 and the diameter of bore 26 is such that an acceleration to a velocity of between 30 feet per second to as high as 1000 feet per second is achieved prior to the point of impingement. An acceleration to a velocity of between and 500 feet per second, for example, can be obtained when a pressurized 10 percent solution of butene-l polymer in butene-l monomer is introduced into a nozzle assembly in which bore 24 is approximately one-half of the diameter of bore 26. When the velocity at the point of impingement is significantly below 30 feet per second, particulation of the polymeric strands is incomplete and snowballing of the polymer may occur resulting in the retention of substantial amounts of solvent in the polymer. Such polymer is known as wet polymer and is normally unsuitable for extrusion. As the polymer velocity is increased to above 1000 feet per second, snowballing again occurs, although for different reasons. At exceptionally high velocities, it is believed that the particle sizes are decreased to a point where the centrifugal force exerted upon the particles is about equal to the force exerted on the solvent vapor, causing the particles and unvaporized solvent to pass through loop 12 at relatively the same velocity. Preferably, the velocity of the gas is maintained at a velocity greater than that of the polymer particles. This is accomplished by exerting a centrifugal force on the polymer particles greater than that exerted on the solvent vapor. This improves polymer drying and solvent vaporization and increases the polymers bulk density. The proper velocity can be maintained by utilizing the nozzle assembly above described with a rate of acceleration therethrough of the polymeric particles of between 200 and 1500 feet per second, or more preferably an acceleration of between 400 and 750 feet per second.

In operation, the polymer solution containing the polymer is generally at a pressure of approximately 50 to 500 p.s.i.g. prior to introduction into the nozzle assembly. If the polymer solution is not already at this pressure, the pressure may be achieved by conventional means. Generally, a pressure of at least 50 p.s.i.g. can be achieved by using a solvent having a vapor pressure above 50 p.s.i.g. under usual polymerization conditions. Solvents such as butane, butene, hexane, and the like, possess such a vapor pressure. For example, the polymerization of butene-l in its own monomer at a temperature of about 80 C. will provide a polymeric solution for introduction into the nozzle assembly having a positive pressure of above 150 p.s.i.g. The polymer solution is then introduced into chamber member 13 in any convenient manner where it is extruded through nozzle 23 and into intermediate tube 25. As a result of this controlled expansion of the solvent, a strand or filament of pliable polymer is formed which has removed therefrom a large proportion of the solvent. The strand or filament extends outwardly during formation and it is discharged out discharge orifice 17 Where it is subjected to further drying action and to certain impingement action, as will now be described.

The discharge rate of both the polymer and the volatilized solvent from orifice 17 of the intermediate tube will be such that the polymer is carried through the loop of discharge tube 12 and into cyclone separator 18. UpOn discharge from orifice 17, the strand or filament of polymer is generally intact. Particulation and further drying thereof occurs during impingement and passage through the loop section of discharge tube 12. During passage through tube 12 the polymer particles are also subjected to a centrifugal force greater than that exerted on the solvent vapor. This force differential maintains the particles in particulate form during transit to and deposit in cyclone 18 and permits a. more complete drying action during passage therethrough.

The polymer solution is normally introduced into the nozzle assembly by a carrying means such as pumps, pressurized feed in lines, and so forth, at an elevated temperature as a result of the production phase, and hence it is also important to cool the end product or the polymer particles. In addition, it is important to cause and maintain the passage of the polymer particles through the curved loop at an optimum velocity. Furthermore, it is important to avoid condensation of the previously volatilized solvent in the loop. To prevent or avoid the foregoing difiiculties with respect to the loop of discharge tube 12, in some embodiments of the invention it is desirable to subject the filament of polymer as it is discharged from the discharge orifice 17 to a pressurized gas which is generally heated to a temperature which would facilitate the drying of the polymer particles. In addition, the heated gas further facilitates the movement of the polymer particles through the curved loop of discharge tube 12 and also minimizes the possibility of the solvent vapor condensing in discharge tube 12. This is provided by forcing a heated gas under pressure through tube 16 and into T and then downwardly through discharge tube 12 past the discharge orifice 17. Any material capable of being volatilized at the temperature of introduction may be used. If a low boiling solvent is used in the polymerization reaction, such solvent can be vaporized and also used as the heated gas.

It will be observed that the loop of discharge tube 12 is a closed loop and provides an impingement surface for the polymer particles as described above. Referring now to FIGURE 4, discharge tube 12 loop is shown in isometric perspective, and hence it may be said that the loop of tube 12 is a closed loop and defines an impingement surface of at least 360 degrees. However, it has been found that the impingement surface of the apparatus may take different forms in certain instances. For example, it has been found that in some embodiments, an arcuate surface defining a radius from about 30 degrees to 2500 degrees is satisfactory. Preferably, though, an arcuate surface defining a radius of at least 90 degrees or from 270 degrees to 1300 degrees is used. Such a discharge or impingement means is shown in FIGURE 5 where alternate discharge tube 27 is shown. In this instance, tube 27 is a closed member and provides an arcuate surface of about 450 degrees for the impingement of the polymer thereagainst during passage downwardly therethrough. It is understood that tube 27 could also be an open channel, so long as the impingement surface is an 6 arcuate surface such that the polymer particles passing therethrough are maintained at velocities for the purposes noted above.

In FIGURE 6, intermediate tube 25 is shown discharging into an arcuate shaped impingement member in the form of an open channel member 28, similarly defining a loop of at least 30 degrees to about 810 degrees. Normally, such a channel member would be contained within a closed housing. The polymer and the volatilized solvent being discharged from the intermediate tube 25 will be of such velocity as to normally carry the polymer particles through the channel member 28 prior to discharge into an appropriate collection member such as cyclone 18. Although an open impingement means in the form of a channel member 28 is satisfactory in some instances, a closed discharge tube of relatively small diameter, such as tube 12 or tube 27 (shown in FIGURES 4 and 5, respectively), is prefered. A closed tube is preferred, particularly where a plurality of such tubes is used in a discharge into one collection means. If it should occur that one of the discharge tubes becomes fouled or otherwise inoperable, it can be removed without shutting down of the other discharge tubes which might be required if open loops were used. Moreover, by having a closed discharge tube, it may be easier to recover the solvent by appropriate condensation techniques and also control the amount of dusting which may be prevalent in the open channel type of member.

It will thus be observed that the art has been provided with a simple, yet economical means, for carrying out the so-called recovery phase of polymer production, i.e., the recovery or removal of the polymer from the solvent. The invention also provides a means for producing polymer particles of uniform size and high bulk density and of overcoming certain of the prior art shortcomings.

By utilizing the process above described, almost any type of solid polybutene polymer which can be dissolved in a solvent may be separated from the solvent and free-flowing particles produced therefrom. To some degree, even tacky polybutene polymer may be separated from a solvent by the process of this invention if a means for rapidly cooling the particulated polymer is provided. In addition, certain copolymers of polybutene wherein the butene molecule is the major constituent of the polymer may also be produced and separated by the apparatus and process of this invention. For example, copolymers of butene-l and an olefin of the general formula RCH=CH whereing R is selected from the group of hydrogen or carbon chain having from 1 to 12 carbon atoms can be used. Normally, the copolymers will contain from 60 to 99.5 mol percent of butene-l and preferably at least mol percent butene-l. Examples of useful copolymers include butene-l and ethylene, butene-l and propylene, butene-l and isobutylene, butene-l and Z-methylbutene-l, butene-l and 4-methylpentene-1, butene-l and styrene, and the like.

This invention is particularly well adapted to solutions of polymeric butene-l in which the polymer has a specific gravity of at least 0.88 at 20 C. and preferably between 0.90 and 0.92, or higher, and a crystallinity of at least 10 percent and preferably a crystallinity of between 35 percent and 60 percent at ordinary atmospheric temperatures.

A useful polymerization method for the production of tacky polybutene polymer can be found in US. Patent No. 2,825,721 issued on Mar. 4, 1958. According to this patent, polymers are obtained by polymerizing olefin compounds in the presence of chromium oxide associated with at least one oxide selected from the group consisting of silica, alumina, zirconia, and thoria. The catalyst is obtained by impregnating a silica-alumina complex with an aqueous solution of a chromium compound convertible to chromium oxide upon heating and calcining same under nonreducing conditions such as in the presence of air, oxygen, CO etc., at a temperature in the range of 750 F. to 1500 F., whereby the chromium compound is converted to chromium oxide in which the chromium is in the hexavalent form. The chromium oxide is present in an amount of at least 0.1 weight percent based on the weight of the total catalyst. The temperature which can be used to carry out the polymerization reaction can vary over a broad range, but normally ranges from 100 F. to 500 F. and preferably ranges between 150 F. and 450 F.

The polymerization process described above is preferably maintained at a pressure high enough to maintain a liquid phase reaction. Normally, a pressure of at least 100 psi. to 300 p.s.i. is required. However, pressures as high as 500 p.s.i. or even 700 p.s.i. can be used, if desired. As a general rule, higher pressures favor the production of high molecular weight polymer with all other conditions being constant. The feed rate can range from 0.1 to liquid hourly space velocities in a liquid phase process with a fixed bed catalyst.

Hydrocarbon diluents, preferably parafiin and/or cycloparafiins, serve as solvents for the polymer products. Among the more useful solvents are the acyclic parafiins having from 3 to 12, and preferably 4 to 8 carbon atoms. Any hydrocarbon diluent which is relatively inert, nondeleterious and liquid under reaction conditions can be utilized. The heavier parafiin diluents generally have a higher solvent power for the polymer than do the lighter ones. The lighter paraflins possess many characteristics which are particularly advantageous if the polymeric solution is to be introduced directly from the reaction vessel into the apparatus as described in the instant invention. It is understood, however, that in most all instances the eatalyst is first removed from the polymeric solution.

The polymerization can be eifected with a fixed bed catalyst or with a mobile catalyst. A frequently preferred method of conducting the polymerization reaction comprises conductiug the feed olefin with a slurry of the comminuted chromium oxide catalyst in suspension in the diluent or solvent. From about 0.001 weight percent of catalyst based on the weight of the diluent is ordinarily used. The catalyst can be maintained in suspension by a mechanical agitation device and/ or by virtue of the velocities of the incoming feed or diluent.

Where the polymer is obtained as 'a slurry, the polymer can be separated from the catalyst by dissolution in a solvent of the type above described usually with the aid of heat and agitation. The stripping catalyst can then be accomplished by oxidizing the residual carbonaceous deposit with a controlled concentration of oxygen in an inert gas by conventional procedures.

A description of useful Ziegler polymerization catalysts for obtaining solid polybutene polymer can be found in the Zeigler et al. patent, U.S. No. 3,113,115, issued on Dec. 3, 1963. The Ziegler et a1. patent discloses the mode of preparing a polymerization catalyst from a transitional metal compound, preferably a halide, and a reducing component consisting normally of a metal alkyl compound. Representative of a transitional metal compound which may be used include those selected from Groups IV-B, V-B and VI-B of the Periodic Table. Included in the preferred species are the titanium halides, for example, titanium tetrachloride, titanium trichloride, and titanium dichloride, and mixtures thereof. Other metal compounds, such as zirconium tetrah'alide, hafnium tetrachloride, vanadium chloride, chromium chloride, tungsten chloride, and the like, are especially useful. Still other transitional metal halides containing halogens selected from the group consisting of bromine, iodine, chlorine, and, in certain instances, fluorine, can also be used.

The reducing component of the Ziegler catalyst composition may be any of a variety of reducing agents. Most common among the reducing agents are organometallic compounds such as triethyl aluminum, aluminum diethyl chloride, aluminum diethyl hydride, alu-,

minum triisobutyl, aluminum triisopropyl, and related compounds. Many other reducing agents, such as lithium aluminum hydride, zinc diethyl hydride, and the like, are described in the literature as useful reducing agents and can also be used. These catalysts are of the now wellknown Ziegler variety.

In the catalytic complex comprising a transitional metal compound and a reducing component, the ratio of constituents may be varied over a relatively broad range. The preferred range depends to a lange extent on the operating conditions, the hydrocarbon to be polymerized, and the choice of catalyst to be used. In a catalyst where one mol of titanium halide is used, the triethyl aluminum compound may be varied from about 0.5 to 5 mols or even 10 mols. In using the above catalyst, a number of procedures may be employed. For example, the catalyst complex may be pre-formed and pre-activated prior to combining the complex with the hydrocarbon feed. In another technique, the catalyst may be combined in an inert solvent and this slurry added to or combined with the hydrocarbon feed. In some instances, the catalyst components may be addeddirectly to the hydrocarbon feed. The polymerization reaction is generally conducted in the presence of an inert organic solvent or in the presence of an excess of monomer. While the catalyst may be prepared at temperatures of a wide range, the catalyst will usually be prepared at a temperature between 30 C. and 150 C. The amount of catalyst may be varied quite widely and may be as low as 0.01 weight percent based on the weight of the monomerto be polymerized, but normally will be in the range of about 0.5 to about 510 weight percent. The polymerization reaction is normally conducted at temperatures below 250 C. and at pressures below 300 atmospheres and usually at temperatures of between 25 C. and 150 C. and at about 1-50 atmospheres.

The polymeric reactions may be conducted in bulk, but usually will be in an inert diluent. Preferred are the inert liquid hydrocarbons, the alkanes, such as propane, butane, pentane, heptane, and the like; however, such materials as isooctane, cyclohexane, benzene, toluene, and the like, are also useful. The polymer formed by the above described processes may then be solidified in freeflowing particulate form with a high bulk density by utilization of the apparatus and process of this invention after stopping the polymerization by deactivating the catalyst as with an alcohol.

In another patent to Seelbach et al., U.S. 2,964,510, issued Dec. 13, 1960, a process is described which is directed specifically to the polymerization of butene-l. According to this patent, the polymerization is conducted with a catalyst which is a complex or'reaction product of an alkyl metal compound, such as diethyl aluminum chloride or aluminum sequichloride (an equal molar mixture of aluminum diethyl chloride and ethyl dichloride) with a compound of titanium, e.-g., titanium tetrachloride.

The temperature to be used in carrying out this polymeriz'ation is generally about 25 C. to 35 C. with a pressure of between one and atmospheres, preferably about 800 p.s.i.g. It is preferable to carry out the polymerization in the presence of a substantial 'amount of liquid diluent which may be an inert aliphatic hydrocarbon preferably having about 6 to 20 carbon atoms or various aromatic hydrocarbons or other inert solvents. The polymerization reaction may also be conducted in the absence of a solvent, i.e., in the presence of only butene-l.

Although any desired method of contacting the butene with the catalyst may be used, a preferred method is to pass the olefin as a gas or vapor or even as a liquid into the catalyst slurry with good agitation. Polymerization occurs and continues at a rate which varies somewhat according to the nature of the polymerization feed, the catalysts, and relative concentrations of both the feed and catalyst in respect to the amount of diluent present.

In preparing the catalyst, the preferred procedure is to make a solution of the desired alkyl metal compound in a suitable solvent, such as n-heptane, and make a separate solution of titanium tetrachloride, also in an inert solvent such as n-heptane, and then mix the two solutions in the desired proportions at room temperature. The mixture of these two catalyst components generally causes the formation of a precipitate which is desirably kept in suspension by agitation. According to Seelbach et al., the mol ratio of the aluminum compound to the titanium compound in the catalyst mixture is generally about 6 mols of aluminum per mol of titanium. If solid high moleculer weight insoluble polymer is desired, diethyl aluminum chloride is normally used. However, if lower molecular weight polymer is desired, then the sesquichloride is normally used.

As is indicated by the prior art, various type solvents may be used as a vehicle for the polymerization reaction. If the polymer is already in solution, such solution may, in most instances, also be used in the apparatus and process heretofore described. However, certain solvents possessing certain properties are particularly useful and are more readily adapted for use in the process and apparatus of this invention. Generally, a solvent having a vapor pressure below 30 atmospheres at 20 C. is employed. Preferably, the solvent will have a boiling point above 50 C. and below 70 C. However, a solvent having a boiling point to about 150 C. can also be used, if desired. A solvent having a boiling point between-10 and 30 C. and a vapor pressure of between 10* and 50 atmospheres at C. and having from 3 to 10 or 3 to 6 carbon atoms is still more preferred. Examples of suitable solvents include propane, n-butane, isobutane, but'ene-l, butene-Z, pentane, hexane, cyclohexane, heptane, and methylchloride. However, other aromatic, aliphatic or cycloaliphatic solvents can be used.

Where the polymer is polybutene-l, suitable organic solvents include those selected from the group consisting of propane, butane, isobutane, butene-l, butene-Z, and mixtures thereof.

Normally, the polymer solution is introduced into the nozzle assembly of this invention under conditions which will permit unhampered flow of the polymeric solution through the nozzle means into an area of reduced pressure. Generally, this unhampered flow can be achieved by introducing the polymeric solution into the nozzle means at a temperature of between 20 C. and 200 C. and under a positive pressure. Under special circumstances, temperatures above 200 C. can be used. Solution temperatures of between 35 C. and 90 C. are however, more generally used.

Although the polymeric solution is normally introduced into the nozzle means at a pressure greater than 50 p.s.i.g., pressures as low as 20 p.s.i.g. to as high as 2000 or even 3000 p.s.i.g. may be used, if desired. Generally, the polymeric solution is maintained at a pressure between 50 p.s.i.g. and 500 p.s.i.g. To a large degree, the choice of temperature and pressure to be used will be determined by the particular solvent in which the polymer is dissolved, the concentration of polymer in the solvent, the rate at which the polymer solution is to be introduced through the nozzle means and into the area of reduced pressure, and so forth.

Variations in any of the above conditions either directly or indirectly affect the rate of vaporization of the solvent. This rate of vaporization in turn controls the velocity of the polymeric strand at the point of impingement. As previously stated, the size of the polymeric particle is determined by the velocity of the polymeric strand at the point of impingement. It can therefore be seen from the above that the operating conditions can be varied over a rather broad range, depending on the size of polymer particles desired, the concentration of polymer in the solution, the type of polymer and solvent 10 employed, and so forth. However, in all situations, it is important and vital to the operation of this invention that the polymer be separated from the solution as polymeric strands and, further, that these polymeric strands be accelerated to a velocity suflicient to cause particulation at the point of'impingement. Almost any combina tion of operating conditions which will accomplish these particular results may be used.

A better understanding of the invention may be obtained by referring to the following illustrative example which is not intended, however, to be unduly limitative of the invention.

Example 1 A nozzle assembly (see FIGURE 3) comprising an upper nozzle having a bore diameter of 0.062 inch and a length of 1.5 inches and an intermediate tube having a diameter of 0.125 inch and a length of 10.5 inches was connected to a coiled tube as shown in FIGURE 1. The recovery system, including the nozzle assembly, utilized in this example was essentially the same as that shown in FIGURE 1 of the drawing. The upper nozzle had a length-diameter ratio of about 25:1. The coiled portion was joined to the nozzle assembly by T 15 through which additional butane-1 vapor was added. The coiled portion had a straight section of approximately 8 inches and a coil of approxmately 450 degrees, forming a coil radius of 1.6 inches. The exit portion of this coiled member was then joined with a cyclone receiver 18 in which the polymer particles were collected. All connections were made with suitable vapor tight fittings. The cyclone receiver was jacket-heated and maintained at a temperature of about 71 C. Butene vapor recovery lines leading back to the reaction system were connected to the cyclone receiver. Suitable temperatures and pressures were maintained by introducing heated (116 C.) butene-l vapors through T 15 and into the nozzle assembly.

A butene polymer solution was prepared by adding about 162 mols of butene-l monomer to a catalyst complex which was prepared by combining 0.019 mol of diethyl aluminum chloride to 0.072 mol of TiCl The butene catalyst mixture was thoroughly agitated and heated to a temperature of about 100 C. at a pressure of about 300 p.s.i. After about 20 percent of the monomer had reacted, the reaction was stopped and the reactor cooled to room temperature. The polymer solution was then Washed with water to remove the catalyst. The remaining portion of the polybutene solution was diluted to a concentration of 12 percent by the addition of butene-l monomer and introduced into the nozzle assembly through upper chamber 13 at a temperature of C. and under a pressure of about 300 p.s.i.g. The polymer solution was metered into the nozzle assembly at a constant rate of about one gallon per minute. As the butene-l polymer solution passed through the upper nozzle into the intermediate tube, the blitene-l monomer was vaporized and the polymer was extruded as a continuous strand or filament, which was then impinged against the wall of the coiled member at approximately a 45-degree angle. The velocity of the polymeric strand at the point of impingement was in excess of 300 feet per second. As the polymer strand was impinged against the coiled or arcuate member, the strand was broken into small uniform particles and passed through the arc-ed member unit where further devolatilization and drying occurred. The particles were separated from the butene-l vapors in the cyclone receiver. A portion of the butene-l vapors was then returned to the polymerization system and a portion was reheated for introduction into the nozzle assembly. The polymeric particles were then removed from the cyclone receiver and had a constant size of between 0.1 to 0.2 inch in diameter. These particles were free flowing and had a relatively high bulk density. The extrudedl polymeric products had no visibly detectable bubbles or other visible imperfections. The physical pro- 11 perties of the extruded polymeric product were determined to be as follows:

Melt index at 190 C. 1.28 Density 0.916 Yield strength, p.s.i 2440 Ultimate strength, p.s.i 3300 Hardness (shore D) 68 Elongation percent 250 The pelletized product obtained therefrom was fabricated into a blown film, using conventional film blowing equipment. No film imperfections or dilferences in film strength were noted in polymer particles obtained by the process heretofore described. In other test runs, stabilizers were added to the polymer solution before the polymer is recovered and before all of the butene-l solvent had been removed. These runs lasted for periods in excess of 48 hours with a steady state of conditions being maintained throughout the polymerization and separating process.

Example 1 was repeated using various polymeric velocities at the point of impingement. The effect that these different velocities had on the polymeric particles is shown in Table I below:

TABLE I Polymer Velocity, Run ft./sec., Partlcle Size At point of Impingement A 300 0.1 inch by up to 0.2 inch.

B 5 0.4 inch by up to 6 inches.

0 1500 0.001 inch by up to 4-5 inches.

Example 2 A butene-l polymer solution was prepared by the process described in Example 1. The bulk density of the polymeric product produced therefrom was compared with bulk densities of polymers obtained by other means known in the art.

TABLE II Run Means of Separating Polymer Bulk Density (lbs/cu. it.)

D Flashing 5.0

E. Precipitation and Drying 3. 0

F-.. Spray Drying 3.6

G Apparatus used in Example 1 10. 6

I claim: 1. The method of separating a free-flowing polybutene polymer from a solvent in a polymer solution comprising extruding the polybutene polymer solution at a positive pressure into an area of reduced pressure to form a filament and achieve partial separation of said panied by a partial separation of polymer from said solvent, and impinging said filament against an arcuate surface to achieve further separation by particulation and volatilization of said solvent. a

3. The method as claimed in claim 1 wherein said arcuate surface defines an arc of at least 45 degrees.

4. The method as claimed in claim 1 including the step of applying a pressurized gas to said polymer filament prior to said impinging step to thereby control the velocity of said impingement and to further volatilize said solvent.

5. The method as claimed in claim 1 wherein said arcuate surface defines a curve of about 360 degrees, whereby said polymer is subjected to a centrifugal force,

thereby forming polymeric particles of substantially uniform size and having an improved bulk density.

6. The method of forming solid polybutene polymer particles from a solution of polymer and solvent comprising extruding said solution at pressure between 50 and 500 p.s.i.g. into an area having a reduced pressure level with respect to said pressurized polymer solution to thereby form said polymer into a filament and to partially volatilize said solvent, contacting said filament with a heated gas for increasing the rate of solvent volatilization and impinging said polymeric strand against an arcuate surface defining at least a degree are to thereby particulate said polymeric filament into particles having an improved bulk density and uniform size;

7. The method of forming solid polybutene-1 polymer particles from a soluition of polymer and solvent comprising extruding said solution at a pressure greater than 50 p.s.i.g. into an area of reduced pressure with respect to said pressurized polymer solution to thereby form said polymer into a filament and to partially volatilize said solvent, accelerating said polymeric filament to a velocity of between 30 to 1000 feet per second, introducing a heated gas into the area of reduced pressure to further volatilize said solvent and to maintain the velocity of said filament and impinging said filament against an arcuate surface defining at least a 90 degree are to thereby particulate said polymeric filament into particles having an improved bulk density and uniform particle size, said velocity at the point of impingement being between 30 to 1000 feet per second.

8. The process of claim 1 wherein the extruding of the polymer solution takes place from a nozzle means having a length to bore diameter ratio of at least 5.

9. The process of claim 2 wherein the extrusion of the polymer solution takes place from a nozzle means having a length to bore diameter ratio of from 8:1 to 50:1.

References Cited UNITED STATES PATENTS 3,042,970 7/1962 Terenzi 264-14 FOREIGN PATENTS 959,353 England.

ROBERT F. WHITE, Primary Examiner.

J. R. HALL, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,373 {235' March 12 1968 Billy D. Rice It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, lines 62, 63 and 64, "per second", each occurrence, should read per second per second Column 6, line 18, "prefered", first occurrence, should read preferred Column 8, line 55, "ethyl dichloride" should read aluminum ethgllggchloride Column 10, line 40, "0.019" should read Signed and sealed this 29th day of July 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr; E. JR. Attesting Office Commissioner of Patents 

